1. Field of the Invention
The present invention relates to a battery of a mobile terminal, and more particularly to a safety device for a battery that improves the safety of the battery by smoothly releasing an internal pressure of the battery when the internal pressure of the battery exceeds a predetermined pressure.
2. Description of the Related Art
A mobile communication terminal can be carried with a user allowing him or her to call another party while moving about. Further, the mobile terminal generally includes a detachable battery for supplying power to the terminal. The battery can also be recharged after it has been used for a certain period of time to thereby reuse the battery.
In addition, a mobile terminal battery is commonly a lithium battery. In the lithium battery, lithium ions are generated by oxidation from poles formed of lithium oxide, and the lithium ions move through an electrolyte and are reduced by reduction from a negative pole formed of material such as carbon or the like, thereby generating electric energy. The generated electric energy is then used to operate the mobile terminal.
For example, FIG. 1 is a perspective view illustrating one example of a related art battery, and FIG. 2 is a perspective illustrating the related battery without a cover member.
As shown in FIGS. 1 and 2, the related art battery includes a hexahedral-shaped cell 100 filled with an electrolyte or the like, and a protection circuit assembly 200 connected to one side of the cell 100. The protection circuit assembly 200 stabilizes a current within the cell 100 when electric discharge or recharge occurs within the cell. Also shown is a cover member 300 surrounding and protecting the protection circuit assembly 200 and reinforcing a coupling force between the protection circuit assembly 200 and the cell 100.
Further, the cell 100 is formed of an aluminum material and is hermetically sealed. The protection circuit assembly 200 also include terminals 210 respectively connected to a terminal portion of the cell 100. In addition, the cover member 300 is formed using a low temperature, lower pressure injection method with resin, such as a synthetic resin of a nylon series, after the protection circuit assembly 200 is connected to the cell 100.
In addition, if an overcharged state or a high temperature state of the battery is maintained while the battery is being used, an internal pressure of the cell 100 increases, which causes the cell 100 to eventually explode after the internal pressure exceeds a certain pressure. The explosion of the battery not only damages the mobile terminal but may also injure the user. Therefore, research is currently being conducted on how to prevent this from happening.
One method of providing a safe battery is shown in FIG. 3. In this method, the cell 100 is provided with a pressure releasing portion 110 for releasing the internal pressure when the pressure of the cell 100 exceeds a set pressure. As shown, the releasing portion 110 is provided on a side surface of the cell 100. Further, the releasing portion 110 is coupled with the protection circuit assembly 200, and has a certain area and a thickness that is smaller than other portions of the cell 100. Namely, the pressure releasing portion 110 is formed via a groove with a certain area and depth formed in one side of the cell 100.
In such a structure, when the internal pressure of the cell 100 is increased, the pressure releasing portion 110 having a relatively small thickness is torn. Thus, the internal pressure of the cell 100 is released before the cell 100 explodes.
However, as shown in FIG. 4, the molten injection material of the cover member 300 is filled in the groove forming the pressure releasing portion 110 and is solidified in an injection molding process to tightly couple the cell 100 and the protection circuit assembly 200 and to encompass the protection circuit assembly 200. Thus, the cover member 300 blocks the pressure releasing portion 110. Further, because the cover member 300 blocks the pressure releasing portion 110, the pressure releasing portion 110 is not normally operated (i.e., is not easily torn), which may cause the cell 100 to explode.